1. Field of the Invention
This invention relates to a radiation image recording and reproducing system. This invention particularly relates to a radiation image recording and reproducing system wherein a stimulable phosphor is exposed to a radiation passing through an object to have a radiation image stored therein, the stimulable phosphor is scanned with stimulating rays which cause it to emit light in proportion to the radiation energy stored, the emitted light is photoelectrically detected and converted to an electric image signal, the electric image signal is processed, and a visible image is reproduced by use of the processed electric image signal.
2. Description of the Prior Art
A radiation image recording and reproducing system using a stimulable phosphor is described, for example, in U.S. Pat. Nos. 4,258,264, 4,276,473 and 4,315,318, U.S. Patent Appln. Ser. No. 220,780, Japanese Unexamined Patent Publication No. 56(1981)-11395, and "Nikkan Kogyo Shinbun" (Daily Industrial Newspaper), Nov. 6, 1982 edition. The radiation image recording and reproducing system comprises the steps of (i) exposing the stimulable phosphor to a radiation such as X-rays passing through an object to have a radiation image stored therein, (ii) scanning the stimulable phosphor with stimulating rays which cause it to emit light in proportion to the radiation energy stored, (iii) photoelectrically detecting the emitted light and converting it into an electric image signal, and (iv) reproducing a visible image by use of the obtained electric image signal. In this system, image recording can be conducted by use of a radiation exposure dose markedly lower than in the conventional radiography using a silver halide photographic material. Further, by processing the electric image signal in various manners, it is possible to obtain a radiation image having a markedly improved image quality, particularly a high diagnostic efficiency and accuracy. Thus this system is very advantageous in practical use, particularly for medical diagnosis.
In order to put the above-mentioned radiation image recording and reproducing system into practice, many problems with regard to practical use must be solved. Thus a radiation diagnostic system useful for medical purposes can be realized only after the problems with regard to practical use are solved one by one. Particularly, when the radiation diagnostic system for medical purposes is used for diagnoses of many patients or many examination objects as in the case of mass medical examinations, the system must be such that the diagnoses of many patients or many examination objects can be carried out correctly at a high efficiency.
As described above, the aforesaid radiation image recording and reproducing system provides high diagnostic performance by appropriately processing the electric image signal obtained by photoelectrically reading out the radiation image stored in the stimulable phosphor. Therefore, image processings must be carried out appropriately according to the type of image recording. That is, most suitable image processing conditions should be selected according to factors such as the portion of the object to be image-recorded (the heart, the chest, or the like), the image recording method (plain image recording, contrasted image recording, subtraction image recording, or the like), and the diagnostic purpose (mass medical examination, close examination, or the like). The image processings embrace all possible image processings for improving the quality of radiation images according to the portion of the object, for example, contrast adjustments, density level adjustments, image gradation processings, frequency processings, and unsharp mask processings. The image processings also embrace image subtraction processings.
Further, in the aforesaid radiation image recording and reproducing system, exposure conditions of the radiation source, such as an X-ray source, should also preferably be adjusted as required with respect to the above-described type of image recording. Specifically, image recording should be conducted under the most suitable radiation exposure conditions by changing, for example, the tube voltage, the tube current, the exposure time, and the focusing point size of the radiation source.
As described above, in the aforesaid radiation image recording and reproducing system, it is desired that the radiation exposure conditions of the radiation source and the image processing conditions be adjusted to the most suitable conditions according to the aforesaid type of image recording. However, when the radiation image recording and reproducing system is continuously used for recording and reproducing radiation images of many patients or examination objects in mass medical examinations or the like, it is troublesome to adjust the radiation exposure conditions and the image processing conditions for each patient or each examination object every time image recording and reproducing are conducted. Also, in such a case, adjustment errors or operation errors readily arise.
Also, when the aforesaid radiation image recording and reproducing system is put into practice, it is of course necessary to record or memorize information on the patients or the examination objects, for example, the sex, the names, the date of image recording, and the portion of the object, in relation to the image information recorded. In practice, the stimulable phosphor used for recording image information in the aforesaid radiation image recording and reproducing system is fabricated into a sheet-like shape, and the stimulable phosphor sheets are provided with identification codes such as bar codes for identifying the stimulable phosphor sheets. Accordingly, the identification codes of the stimulable phosphor sheets are memorized in relation to the aforesaid object information, and used to clarify the relationship between the image information recorded in the stimulable phosphor sheets and the object information at the time of image recording and reproducing. The operations for correctly clarifying the relationship between the object information and the identification codes and for memorizing the object information and the identification codes in relation to each other are not always possible to conduct when a large number of objects have to be handled. Thus there is a risk of mistakes arising in such operations. However, the aforesaid operation must be carried out without fail for all objects. This problem must also be solved in practical use of the radiation image recording and reproducing system.